Litres are a measure of volume (like pints), whereas tonnes are a measure of mass, also often wrongly referred to as weight. So it depends on the density of the substance. If it is water it is easy - 1 litre = 1 kg, so 1000 litres = 1000kg = 1 tonne. A tonne is 1000kg. If you know the density of your substance relative to water you can convert from there. For example if density is 1/2 that of water 1000 litres = 500kg = 0.5 tonnes.

Are you filling raised beds or something? And what kind of compost is it?

No I am trying to work out if it is cheaper for me and my family to buy a tonne of compost for this year rather than buy the MPC which is on offer. I want to know how many bags we would get from a tonne and how much it would cost. If, for example, its 100 bags then that will be too much, but if it worked out to be 20 bags then it could be better value. I didn't want to get my neighbours hopes up without trying to work it out first.

It is MPC.

Aberdeen plotter if you hadn't said then I would have given you all the credit. Maybe the answer is to weigh a litre of MPC and see what that gives me.

Aberdeen plotter if you hadn't said then I would have given you all the credit. Maybe the answer is to weigh a litre of MPC and see what that gives me.

But then I couldn't have lived with the knowledge that I had plageurised some poor souls work.

Don't know if this helps but I make up my compost for growing exhibition potatoes and then store it in tonne builders bags until I do the planting. Each builders bag filled to the top holds 35 x 17 ltre bags of compost. That is a few litres short of 600ltres or 7.5 x 80 ltre bags.

That comparison is by volume and not by weight so a weight comparison would be useful.

Remember you may have difficulty transporting compost in bulk whereas you can easily move a few 80 ltre bags.

How ever many bags make up a ton(ne), £1.40 for 80L of MPC is a real bargain.
Also remember that commercial MPC bags state the volume 'when packed'. Both the volume and the weight change with storage and the state of hydration.